The present invention relates to a cooling apparatus for electronic elements, and more particularly, to a cooling apparatus which is suitable to cool semiconductor elements such as transistors and thyristers.
Examples of the apparatus for cooling the electronic elements such as transistor and thyrister by radiating heat generated therefrom are disclosed in Japanese Patent Unexamined Publication Nos. 63-254754 and 1-192148. The cooling apparatus disclosed in the latter publication comprises an electronic device, a metallic block which serves as a heatsink of the electronic device, a plurality of heat pipes each extending in the vertical direction with one end thereof inserted in the metallic block and having a plurality of horizontal cooling fins provided at the other end thereof, a thermal conductive electric insulator disposed between the electronic device and the metallic block, conductor metals formed integrally with the thermal conductive electric insulator or both surfaces thereof, a duct which envelops the cooling fins, and a fan to supply cold wind to the duct. The thermal conductive electric insulator having the conductor metals formed integrally therewith, the electronic device and the metallic block are kept in pressure contact with each other or bonded together by means of bonding agent.
Heat of the electronic device is transferred to the metallic block through the conductor metal, the thermal conductive electric insulator and the other conductor metal. Heat transferred to the metallic block is transferred to a refrigerant sealingly contained in the heat pipes and it evaporates the refrigerant. The evaporated refrigerant moves upwards within the heat pipes to the other ends thereof where the radiation fins are provided. At the other ends, heat is removed by the cold wind supplied by the fan, so that the refrigerant is liquefied and returned to the one ends of the heat pipes. In this way, heat of the electronic device is dissipated into the air.
In the cooling apparatus described above, since the thermal conductive electric insulator having the conductor metals formed integrally on the both surfaces thereof, the electronic device and the metallic block are bonded together by means of the bonding agent, when it becomes necessary to change the design of the electronic device, the whole device cooling apparatus must be remodeled, resulting in that the apparatus is very uneconomical and has little flexibility to change of the design.
In case that the thermal conductive electric insulator having the conductor metals formed integrally on the both surfaces thereof, the electronic device and the metallic block are kept in pressure contact with each other, it is possible to change only the electronic device, and however, there arises a problem that the positioning between the electronic device the design of which is changed and the metallic block is not easy actually. Further, in the case of being kept in pressure contact, contact thermal resistance is generated between the pressure contact surfaces of the electronic device and the conductor metal and between the pressure contact surfaces of the conductor metal and the metallic block, resulting in a problem that the thermal conductivity is deteriorated.
In addition, since the radiation fins extend in the horizontal direction, the air warmed by the radiation fins is hindered from moving upwards by the radiation fins themselves. For this reason, heat radiation by natural convection is not sufficient and, hence, the fan for the forced cooling is required.
Moreover, since the heat pipes extend in the vertical direction, there is a problem that the heightwise length of the cooling apparatus is increased. Further, in case that the calorific value of the electronic device is large, it is necessary to increase the radiation capacities of the metallic block and the heat pipes. In this case, however, the widthwise length of the metallic block and the number of the heat pipes must be increased, resulting in a problem that the widthwise length of the cooling apparatus is increased.